Resisting the urge to eat more than you need. Reducing portions helps too. This is easier said than done and it takes effort. It means you must stop eating after you've finished your allotted amount, but that takes will power.
Also, not grabbing for that bit of comforting food when you are down and need comforting; grab a favorite book and start reading is best. Or turn on the computer and read hubs on how to stay healthy!